Methods for reducing ischemia-reperfusion injury via targeted control of blood gases

ABSTRACT

Provided herein are methods for reducing ischemia-reperfusion injury and/or microvascular obstructions by administering to the subject effective amounts of carbon dioxide and oxygen before, during and/or after re-establishing perfusion. In some embodiments, the methods further include using therapeutic hypothermia.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of International Application No. PCT/US2014/049832 filed Aug. 5, 2014, which designated the U.S. and that International Application was published under PCT Article 21(2) in English, which claims priority under 35 U.S.C. § 119(e) to U.S. provisional patent application No. 61/862,211 filed Aug. 5, 2013, the contents of each of which are herein incorporated by reference in their entirety.

FIELD OF INVENTION

The invention is directed to methods for reducing ischemia-reperfusion injury in a subject in need thereof by delivering increased volumes of less oxygenated blood during reperfusion by controlling the delivery of oxygen and carbon dioxide in arterial blood.

BACKGROUND

All publications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Myocardial infarction (MI) or acute myocardial infarction (AMI), commonly known as a heart attack is the interruption of blood supply to a part of the heart, causing heart cells to die. Myocardial infarction is caused by ischaemic or ischemic heart disease (IHD), or myocardial ischaemia, which is characterized by reduced blood supply due to a partial or complete blockage of an artery that carries blood to the heart, usually due to coronary artery disease (atherosclerosis of the coronary arteries). The decrease in blood flow reduces the heart's oxygen supply. Myocardial ischemia is an imbalance between myocardial oxygen supply and demand. Its risk increases with, for example, age, smoking, hypercholesterolaemia (high cholesterol levels), diabetes, and hypertension (high blood pressure), and is more common in men and those who have close relatives with ischaemic heart disease. Myocardial ischemia is the pathological state underlying ischaemic heart disease.

In the event of a myocardial infarction, maximizing myocardial salvage from regions of pronounced ischemia in patients suffering an infarction is the most important goal of any therapeutic strategy delivered to the patient. The therapeutic standard for countering the acute ischemic burden is the re-establishment of blood flow, while reducing ischemia-reperfusion injury, via percutaneous transluminal coronary angioplasty (PTCA), coronary artery bypass grafting (CABG) or fibrinolysis. Of these two approaches, the most sought after therapeutic regiment is PTCA. Reperfusion therapies do not always re-establish flow and can lead to microvascular obstructions (MVOs). It has been shown that MVOs occur at the site of severe ischemic injury and that they have been associated with poor prognosis and reduced survival rates in the months and years post reperfusion. It is also known that MVOs are associated with larger infarcts and that larger infarcts lead to poorer remodeling in the chronic stage of disease culminating in heart failure. Since heart failure is a growing epidemic in the Western World, and most heart failures have origins in ischemic heart disease it is desirable to reduce ischemia-reperfusion injury in right at the acute setting.

Reperfusion can cause further damage and cell death, resulting in ischemia/reperfusion injury (IRI). There are no established drugs to prevent or treat IRI. A major cause of myocardial damage/death from IRI is a superoxide burst at reperfusion. Given the problems associated with existing reperfusion therapies, such as microvascular obstructions, there is a need in the art for reperfusion therapies that restore blood flow to the ischemic regions of the heart without any injuries to said region.

SUMMARY OF THE INVENTION

Described herein are methods for reducing and/or inhibiting ischemia-reperfusion injury in a subject in need thereof. Also described are methods for reducing or inhibiting microvascular obstructions and/or reducing hemorrhagic microvascular in a subject in need thereof.

The methods include administering to the subject a first admixture comprising carbon dioxide in an amount to achieve a predetermined partial pressure of carbon dioxide (PaCO₂), a second admixture comprising oxygen in an amount to achieve a predetermined partial pressure of oxygen (PaO₂) and re-establishing perfusion using, for example, percutaneous transluminal coronary angioplasty, CABG or fibrinolysis. The methods may further include establishing therapeutic hypothermia by cooling blood prior to reperfusion.

DETAILED DESCRIPTION OF THE INVENTION

All references cited herein are incorporated by reference in their entirety as though fully set forth. Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Singleton et al., Dictionary of Microbiology and Molecular Biology 3^(rd) ed., J. Wiley & Sons (New York, N.Y. 2001); March, Advanced Organic Chemistry Reactions, Mechanisms and Structure 5^(th) ed., J. Wiley & Sons (New York, N.Y. 2001); and Sambrook and Russel, Molecular Cloning: A Laboratory Manual 3rd ed., Cold Spring Harbor Laboratory Press (Cold Spring Harbor, N.Y. 2001), provide one skilled in the art with a general guide to many of the terms used in the present application.

One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present invention. Indeed, the present invention is in no way limited to the methods and materials described. For purposes of the present invention, the following terms are defined below.

“Route of administration” or “administering” may refer to any administration pathway known in the art, including but not limited to aerosol, nasal, oral, inhalation, transmucosal, transdermal, parenteral or enteral. “Parenteral” refers to a route of administration that is generally associated with injection, including intraorbital, infusion, intraarterial, intracapsular, intracardiac, intradermal, intramuscular, intraperitoneal, intrapulmonary, intraspinal, intrasternal, intrathecal, intrauterine, intravenous, subarachnoid, subcapsular, subcutaneous, transmucosal, or transtracheal.

“Beneficial results” may include, but are in no way limited to, lessening or alleviating the severity of the disease condition, preventing the disease condition from worsening, curing the disease condition, preventing the disease condition from developing, lowering the chances of a patient developing the disease condition and prolonging a patient's life or life expectancy.

“Mammal” or “subject” as used herein refers to any member of the class Mammalia, including, without limitation, humans and nonhuman primates such as chimpanzees and other apes and monkey species; farm animals such as cattle, sheep, pigs, goats and horses; domestic mammals such as dogs and cats; laboratory animals including rodents such as mice, rats and guinea pigs, and the like. The term does not denote a particular age or sex. Thus, adult and newborn subjects, as well as fetuses, whether male or female, are intended to be included within the scope of this term.

“Treatment” and “treating,” as used herein refer to both therapeutic treatment and prophylactic or preventative measures, wherein the object is to prevent or slow down (lessen) the targeted pathologic condition, prevent the pathologic condition, pursue or obtain beneficial results, or lower the chances of the individual developing the condition even if the treatment is ultimately unsuccessful. Those in need of treatment include those already with the condition as well as those prone to have the condition or those in whom the condition is to be prevented.

“Ischaemia” or “Ischemia” as used herein refers to reduced blood supply to a tissue and/or an organ. Ischemic heart disease refers to reduced blood supply to the heart due to a partial or complete blockage of an artery that carries blood to the heart.

“Reperfusion” as used herein refers to re-establishing perfusion to an ischemic area and/or organ.

“Pain to balloon time” as used herein refers to the time between the onset of symptoms of myocardial infarction up to the angioplasty.

“Effective amount” or “in an amount” as used herein refers to, for example, the amount of O₂ or CO₂ administered to the subject so as to reach a predetermined partial pressure of O₂ or CO₂, respectively.

Under normal conditions, humans breathe air that is about 21% oxygen. Current ischemia-reperfusion methods include use of 100% oxygen. The inventors hypothesize that ischemia reperfusion injury may be reduced in a subject by administering larger volumes of less oxygenated blood. This may be achieved by administering an effective amount of carbon dioxide and oxygen so as to reach predefined levels of arterial pressure of carbon dioxide and oxygen. Carbon dioxide, as a vasodilator, allows increased volumes of less oxygenated blood to be delivered to the target region.

Described herein are methods for reducing and/or inhibiting ischemia-reperfusion injury in a subject in need thereof. Also described are methods for reducing and/or inhibiting microvascular obstructions and/or reducing hemorrhagic microvascular in a subject in need thereof. The methods include administering to the subject a first admixture comprising carbon dioxide in an amount to achieve a predetermined partial pressure of carbon dioxide (PaCO₂), a second admixture comprising oxygen in an amount to achieve a predetermined partial pressure of oxygen (PaO₂) and re-establishing perfusion using, for example, percutaneous transluminal coronary angioplasty, CABG or fibrinolysis. In some embodiments, the first and second admixtures are administered concurrently. In further embodiments, the first and second admixtures are administered sequentially. In some embodiments, the oxygen source is room air. In some embodiments, the first and/or second admixtures are administered before, during and/or after percutaneous transluminal coronary angioplasty, CABG or fibrinolysis.

Also described herein are methods for reducing and/or inhibiting ischemia-reperfusion injury in a subject in need thereof. Also provided are methods for reducing and/or inhibiting microvascular obstructions and/or reducing hemorrhagic microvascular in a subject in need thereof. The methods include promoting vasidilation by administering to the subject an admixture comprising carbon dioxide in an amount to achieve a predetermined partial pressure of carbon dioxide (PaCO₂) and re-establishing perfusion using, for example, percutaneous transluminal coronary angioplasty, CABG or fibrinolysis. In some embodiments, in addition to CO₂, O₂ may also be administered. In an embodiment, the oxygen source is room air. In some embodiments, CO₂ and optionally O₂ are administered before, during and/or after percutaneous transluminal coronary angioplasty, CABG or fibrinolysis.

Further described are methods for reducing and/or inhibiting ischemia-reperfusion injury in a subject in need thereof. The invention also provides methods for reducing and/or inhibiting microvascular obstructions and/or reducing hemorrhagic microvascular in a subject in need thereof. The methods include administering to the subject admixture comprising oxygen in an amount to achieve a predetermined partial pressure of oxygen (PaO₂) and re-establishing perfusion using, for example, percutaneous transluminal coronary angioplasty, CABG or fibrinolysis. In some embodiments, in addition to O₂, CO₂ may also be administered. In an embodiment, the oxygen source is room air. In some embodiments, O₂ and optionally CO₂ are administered before, during and/or after percutaneous transluminal coronary angioplasty, CABG or fibrinolysis.

The methods described herein may further comprise establishing therapeutic hypothermia by cooling blood prior to reperfusion and/or during reperfusion. In some embodiments, establishment of reperfusion may include PTCA or fibrinolysis. Reperfusion may be established using cooled blood and concurrently or sequentially administering to the subject a first admixture comprising carbon dioxide in an amount to achieve a predetermined partial pressure of carbon dioxide (PaCO₂) and/or administering to the subject a second admixture comprising oxygen in an amount to achieve a predetermined partial pressure of oxygen (PaO₂). In some embodiments, the first and second admixtures are administered concurrently. In further embodiments, the first and second admixtures are administered sequentially.

Provided herein is a system for reducing ischemia-reperfusion injury in a subject in need thereof comprising a computerized gas control delivery systems adapted to provide a first admixture comprising carbon dioxide in an amount to reach a predetermined partial pressure of carbon dioxide to induce hyperemia and a second admixture comprising oxygen in an amount to reach a predetermined partial pressure of oxygen so as to deliver less oxygenated blood. In various embodiments, computerized gas control delivery systems include but are not limited to feedback to bend tidal gas concentration (also known as end-tidal forcing system) and prospective end-tidal targeting system (for example RespirACT™).

In some embodiments, therapeutic hypothermia is established via surface cooling of the blood or via delivering cooled blood using a catheter through the femoral artery. In various embodiments, the blood is cooled to 2-7° C. lower than the normal systemic, 2-5° C. lower than the normal systemic, 2-3° C. lower than the normal systemic, 4-7° C. lower than the normal systemic and/or 5-7° C. lower than the normal systemic. In some embodiments, the blood is cooled to temperatures described herein in myocardial infarction patients whose treatment is initiated, for example, at least 2 hours, at least 3 hours, at least 4 hour, at least 5 hours or at least 6 hours, after the onset of symptoms of myocardial infarction.

In some embodiments, symptoms of myocardial infarction include but are not limited to any one or more of chest pain, elevated FP segment in an electrocardiogram (ECG) and/or elevated troponin levels in the blood. Chest pains may be accompanied by shortness of breath, dizziness or lightheadedness, jaw pain, nausea/vomiting, unusual fatigue, cold sweat and/or pain in the arm, back, neck, abdomen, and or shoulder blades.

In some embodiments, oxygen and carbon dioxide are administered concurrently to reach pre-determined levels of partial pressures of oxygen and carbon dioxide in the arteries, during re-establishing reperfusion. In other embodiment, oxygen and carbon dioxide are administered sequentially to reach pre-determined levels of partial pressures of oxygen and carbon dioxide in the arteries, during re-establishing reperfusion. In an alternate embodiment, the subject breathes normal air concurrently with administration of carbon dioxide. In an embodiment, carbon dioxide and/or oxygen are delivered via inhalation.

In some embodiments, the extent of ischemia-reperfusion injury may be fully evaluated on the basis of MRI. Cine MRI can be used to estimate left-ventricular ejection fraction (LVEF)¹, which is a measure of global cardiac function, and estimate wall-motion anomalies² due to infarction. T2-weighted MRI can be used to estimate the extent of myocardial edema³ in the acute setting and late-gadolinium enhancement MRI⁴ can be used to characterize the infarction (size, location and transmurality). Collectively these measures allow one to estimate the extent IR injury at the acute, subacute and chronic phases of infarction. The extent of injury and the associated cardiac changes can also be evaluated and serially followed with other medical imaging modalities such as echocardiography, computed tomography (CT), single photon emission tomography (SPECT) and positron emission tomography.

In various embodiments, computerized gas control delivery systems may be used with the methods described herein including but not limited to feedback to bend tidal gas concentration (also known as end-tidal forcing system) and prospective end-tidal targeting system (for example RespirACT™). In some embodiments of the methods described herein, the CO₂ is delivered from a computerized gas control delivery system and the source of oxygen is room air. In some embodiments of the methods described herein, O₂ and CO₂ are delivered from an apparatus which includes valves that regulate the flow of the gases from the gas tanks In some embodiments, changes in breathing patterns established through voluntary (for example, by asking the subject to hold their breath for a period or hyperventilating over a period of time that is comfortable for the patient) means are used to modulate the partial pressure of O₂ and CO₂ of the blood traversing the coronary circulation.

In any organ system where ischemia is preceded by reperfusion, the proposed method is expected to reduce the tissue injury associated with re-establishment of perfusion with excessive oxygenation and suboptimal capillary recruitment. For example, the proposed method is expected to reduce ischemia-reperfusion injury in brain where treatment to resolve ongoing ischemia is mitigated via stenting of cerebral or extracaranial (carotid) arteries. Alternatively, when reperfusion is not limited to a single vessel but to whole organs (such as transplantation of heart, lungs, liver, kidney etc.), the proposed approach is expected to reduce the global injury to the transplanted organ, enhancing the long-term viability of the transplanted organ.

In some embodiments, “reduce”, “reducing” and/or “reduction” of reperfusion injury as described herein refers to decrease in reperfusion injury relative to one or more reference values. In one embodiment, the reference values may be based on established standards of the scar size and/or LVEF parameters observed when the methods described herein are not used during reperfusion. In another embodiment, the reference values may be based on established standards of the scar size and/or LVEF parameters observed when 100% O₂ is used during reperfusion. In various embodiments, the reduction in reperfusion injury is about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100% reduction in scar size and/or LVEF relative to the reference value. In some embodiments, the percentage reduction in scar size may be about the same as the percentage reduction in LVEF. In other embodiments, the percentage reduction in scar size may be different than the percentage reduction in LVEF. In various embodiments, the reduction in reperfusion injury is about 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 10-fold, 15-fold, 20-fold, 25-fold, 30-fold, 35-fold, 40-fold, 45-fold, 50-fold, 55-fold, 60-fold, 65-fold, 70-fold, 75-fold, 80-fold, 85-fold, 90-fold, 95-fold, 100-fold or a combination thereof. In some embodiments, the fold reduction in scar size may be about the same as the fold reduction in LVEF. In other embodiments, the fold reduction in scar size may be different than the fold reduction in LVEF.

In some embodiments, the admixture comprising CO₂ is administered at high doses for short duration or at low doses for longer durations. For example, administering the admixture comprising CO₂ at high doses of CO₂ for a short duration comprises administering any one or more of 40 mmHg to 45 mmHg, 45 mmHg to 50 mmHg, 50 mmHg to 55 mmHg, 55 mmHg CO₂ to 60 mm Hg CO₂, 60 mmHg CO₂ to 65 mm Hg CO₂, 65 mmHg CO₂ to 70 mm Hg CO₂, 70 mmHg CO₂ to 75 mm Hg CO₂, 75 mmHg CO₂ to 80 mm Hg CO₂, 80 mmHg CO₂ to 85 mm Hg CO₂ or a combination thereof, for about 20 minutes, 15 minutes, 10 minutes, 9 minutes, 8 minutes, 7 minutes, 6 minutes, 5 minutes, 4 minutes, 3 minutes, 2 minutes, 1 minute or a combination thereof. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

For example, administering low doses of predetermined amounts of CO₂ for a longer duration comprises administering the predetermined amount of CO₂ at any one or more of about 30 mmHg CO₂ to about 35 mmHg CO₂, about 35 mmHg CO₂ to about 40 mmHg CO₂, about 40 mmHg CO₂ to about 45 mmHg CO₂ or a combination thereof for any one or more of about 20 to 24 hours, about 15 to20 hours, about 10 to 15 hours, about 5 to 10 hours, about 4 to 5 hours, about 3 to 4 hours, about 2 to 3 hours, about 1 to 2 hours, or a combination thereof, before inducing hyperemia. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In one embodiment, CO₂ is administered in a stepwise manner. In another embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 5 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In another embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 10 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In a further embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 20 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In a further embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 30 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In a further embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 40 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In a further embodiment, administering carbon dioxide in a stepwise manner includes administering carbon dioxide in 50 mmHg increments in the range of any one or more of 10 mmHg to 100 mmHg CO₂, 20 mmHg to 100 mmHg CO₂, 30 mmHg to 100 mmHg CO₂, 40 mmHg to 100 mmHg CO₂, 50 mmHg to 100 mmHg CO₂, 60 mmHg to 100 mmHg CO₂, 10 mmHg to 90 mmHg CO₂, 20 mmHg to 90 mmHg CO₂, 30 mmHg to 90 mmHg CO₂, 40 mmHg to 90 mmHg CO₂, 50 mmHg to 90 mmHg CO₂, 60 mmHg to 90 mmHg CO₂, 10 mmHg to 80 mmHg CO₂, 20 mmHg to 80 mmHg CO₂, 30 mmHg to 80 mmHg CO₂, 40 mmHg to 80 mmHg CO₂, 50 mmHg to 80 mmHg CO₂, 60 mmHg to 80 mmHg CO₂, 10 mmHg to 70 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 70 mmHg CO₂, 30 mmHg to 70 mmHg CO₂, 40 mmHg to 70 mmHg CO₂, 50 mmHg to 70 mmHg CO₂, 60 mmHg to 70 mmHg CO₂, 10 mmHg to 60 mmHg CO₂, 20 mmHg to 60 mmHg CO₂, 30 mmHg to 60 mmHg CO₂, 40 mmHg to 60 mmHg CO₂ or 50 mmHg to 60 mmHg CO₂. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 5 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 10 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 20 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 30 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 40 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

In some embodiments, administering oxygen in a stepwise manner includes administering oxygen in 50 mmHg increments in the range of any one or more of 30 mmHg to 100 mmHg O₂, 50 mmHg to 100 mmHg O₂, 70 mmHg to 100 mmHg O₂, 90 mmHg to 100 mmHg O₂, 30 mmHg to 200 mmHg O₂, 50 mmHg to 200 mmHg O₂, 70 mmHg to 200 mmHg O₂, 90 mmHg to 200 mmHg O₂, 150 mmHg to 200 mmHg O₂, 30 mmHg to 300 mmHg O₂, 50 mmHg to 300 mmHg O₂, 100 mmHg to 300 mmHg O₂, 150 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 200 mmHg to 300 mmHg O₂, 250 mmHg to 300 mmHg O₂, 30 mmHg to 400 mmHg O₂, 50 mmHg to 400 mmHg O₂, 100 mmHg to 400 mmHg O₂, 150 mmHg to 400 mmHg O₂, 200 mmHg to 400 mmHg O₂, 250 mmHg to 400 mmHg O₂, 300 mmHg to 400 mmHg O₂, 350 mmHg to 400 mmHg O₂, 30 mmHg to 500 mmHg O₂, 500 mmHg to 500 mmHg O₂, 100 mmHg to 500 mmHg O₂, 150 mmHg to 500 mmHg O₂, 200 mmHg to 500 mmHg O₂, 250 mmHg to 500 mmHg O₂, 300 mmHg to 500 mmHg O₂, 350 mmHg to 500 mmHg O₂, 400 mmHg to 500 mmHg O₂ or 450 mmHg to 500 mmHg O₂.

Other increments of carbon dioxide and oxygen to be administered in a stepwise manner will be readily apparent to a person having ordinary skill in the art.

In some embodiment, a predetermined combination of partial pressure of carbon dioxide and/or oxygen prior to re-establishing perfusion will be administered so as to adapt the subject for reperfusion. Block administration of carbon dioxide and/or oxygen comprises administering carbon dioxide and/or oxygen in alternating amounts over a period of time.

Alternating amounts of CO₂ comprises alternating between any of 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg of carbon dioxide. In various embodiments, the predetermined levels of CO₂ are administered so that the arterial level of CO₂ reaches the PaCO₂ of any one or more of the above ranges. Other amounts of carbon dioxide to be used in alternating amounts over a period of time will be readily apparent to a person having ordinary skill in the art.

Alternating amounts of O₂ comprises alternating between any of 5 mmHg and 100 mgHg, 20 mmHg and 100 mmHg, 30 mmHg and 100 mmHg, 40 mmHg and 100 mmHg, 50 mmHg and 100 mmHg, 60 mmHg and 100 mmHg, 70 mmHg and 100 mmHg, 80 mmHg and 100 mmHg, 90 mmHg and 100 mmHg, 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg of oxygen. In various embodiments, the predetermined levels of O₂ is administered so that the arterial level of O₂ reaches the PaO₂ of any one or more of the above ranges. Other amounts of oxygen to be used in alternating amounts over a period of time will be readily apparent to a person having ordinary skill in the art.

EXAMPLES Example 1

Canines (n=9) underwent left thoracotomy at the 4^(th) intercostal space and a hydraulic occluder was secured around the left-anterior descending coronary artery after the first principal diagonal. Subsequently a Doppler flow probe was affixed distal to the hydraulic occluder and animals were allowed to recover for 7 days. Following recovery, animals were subjected to ischemia/reperfusion (I/R) protocol and studied with magnetic resonance imaging. The ischemia protocol consisted of inflicting no-flow ischemia by inflating the hydraulic occlude (confirmed by the Doppler flow velocity) for 3 hours. Subsequently all animals were reperfused by deflation of the hydraulic occluder. During ischemia all animals were intubated and mechanically ventilated with ventilator with 100% O₂. In a fraction the animals (n=5), during reperfusion the ventilation with 100% O₂ was maintained, while remainder of the animals (n=4) were allowed to breathe room air.

Animals were imaged on a 3.0 T Siemens MRI system and left-ventricular ejection fraction and scar volume as a percentage of the left ventricular volume were computed at week 8, post I/R injury, based on previously published methods^(1,4).

TABLE 1 Scar Volume at week 8 LVEF at week 8 post MI (% LV) post MI Animals breathing 100% O₂ 15.0 +/− 3.8 39.7 +/− 4.9 during reperfusion Animals breathing room air 11.2 +/− 3.6 45.2 +/− 3.6 during reperfusion

These results show that animals receiving 100% O₂ during reperfusion had worse outcomes (larger scar size) and poorer remodeling (lower ejection fraction) than those animals breathing room air during reperfusion. In particular, these studies showed that the chronic scar size was approximately 25% larger and the left ventricular ejection fraction (LVEF) was reduced by 12% in animals receiving 100% O₂ versus those that were breathing room air during the reperfusion.

Various embodiments of the invention are described above in the Detailed Description. While these descriptions directly describe the above embodiments, it is understood that those skilled in the art may conceive modifications and/or variations to the specific embodiments shown and described herein. Any such modifications or variations that fall within the purview of this description are intended to be included therein as well. Unless specifically noted, it is the intention of the inventors that the words and phrases in the specification and claims be given the ordinary and accustomed meanings to those of ordinary skill in the applicable art(s).

The foregoing description of various embodiments of the invention known to the applicant at this time of filing the application has been presented and is intended for the purposes of illustration and description. The present description is not intended to be exhaustive nor limit the invention to the precise form disclosed and many modifications and variations are possible in the light of the above teachings. The embodiments described serve to explain the principles of the invention and its practical application and to enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out the invention.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects. It will be understood by those within the art that, in general, terms used herein are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

REFERENCES

-   1. Can J C, Simonetti O, Bundy J, Li D, Pereles S, Finn J P. Cine M     R angiography of the heart with segmented true fast imaging with     steady-state precession. Radiology. 2001 June; 219(3):828-34. -   2. Kachenoura N, Redheuil A, Balvay D, Ruiz-Dominguez C, Herment A,     Mousseaux E, Frouin F. Evaluation of regional myocardial function     using automated wall motion analysis of cine MR images: Contribution     of parametric images, contraction times, and radial velocities. J     Magn Reson Imaging. 2007 October; 26(4):1127-32. -   3. Abdel-Aty, H., et al., Delayed enhancement and T2-weighted     cardiovascular magnetic resonance imaging differentiate acute from     chronic myocardial infarction. Circulation, 2004. 109(20): p.     2411-6. -   4. Kim R J, Fieno D S, Parrish T B, et al. Relationship of MRI     delayed contrast enhancement to irreversible injury, infarct age,     and contractile function. Circulation 1999; 100(19): 1992-2002. 

What is claimed is:
 1. A method for reducing or inhibiting ischemia-reperfusion injury in a subject in need thereof comprising: (i) administering to the subject a first admixture comprising carbon dioxide in an amount to reach a predetermined partial pressure of carbon dioxide to induce hyperemia; (ii) administering to the subject a second admixture comprising oxygen in an amount to reach a predetermined partial pressure of oxygen; (iii) administering oxygen in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion, wherein administering oxygen in a block-wise manner comprises alternating the amounts of oxygen administered between any of 5 mmHg and 100 mgHg, 20 mmHg and 100 mmHg, 30 mmHg and 100 mmHg, 40 mmHg and 100 mmHg, 50 mmHg and 100 mmHg, 60 mmHg and 100 mmHg, 70 mmHg and 100 mmHg, 80 mmHg and 100 mmHg, 90 mmHg and 100 mmHg, 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg of oxygen; and (iv)re-establishing perfusion to an ischemic area, so as to reduce or inhibit ischemia-reperfusion injury in the subject.
 2. The method of claim 1, further comprising establishing therapeutic hypothermia by cooling blood prior to reperfusion.
 3. The method of claim 2, wherein therapeutic hypothermia is established via surface cooling or via the use of a catheter through the femoral artery.
 4. The method of claim 2, wherein the blood is cooled to 2-7° C. lower than the normal systemic temperature.
 5. The method of claim 1, further comprising administering carbon dioxide in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion.
 6. The method of claim 5, wherein administering carbon dioxide in a block-wise manner comprises alternating the amounts of carbon dioxide administered between any of 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg.
 7. The method of claim 1, further comprising monitoring reperfusion injury or microvascular obstructions using magnetic resonance imaging during reperfusion and post-reperfusion.
 8. The method of claim 1, wherein perfusion is re-established using any one or more of fibrinolytic therapy, angioplasty or CABG.
 9. The method of claim 8, wherein the first and second admixtures are administered before, during and/or after re-establishing perfusion.
 10. The method of claim 1, wherein the first and second admixtures are administered concurrently.
 11. The method of claim 1, wherein the first and second admixtures are administered sequentially.
 12. The method of claim 1, wherein the subject has ischemic heart disease or myocardial ischemia.
 13. A method for reducing microvascular obstructions in a subject in need thereof comprising: (i) administering to the subject a first admixture comprising carbon dioxide in an amount to reach a predetermined partial pressure of carbon dioxide to induce hyperemia; (ii) administering to the subject a second admixture comprising oxygen in an amount to reach a predetermined partial pressure of oxygen; (iii) administering oxygen in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion, wherein administering oxygen in a block-wise manner comprises alternating the amounts of oxygen administered between any of 5 mmHg and 100 mgHg, 20 mmHg and 100 mmHg, 30 mmHg and 100 mmHg, 40 mmHg and 100 mmHg, 50 mmHg and 100 mmHg, 60 mmHg and 100 mmHg, 70 mmHg and 100 mmHg, 80 mmHg and 100 mmHg, 90 mmHg and 100 mmHg, 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg of oxygen; and (iv)re-establishing perfusion to an ischemic area, so as to reduce microvascular obstructions in the subject.
 14. The method of claim 13, further comprising establishing therapeutic hypothermia by cooling blood prior to reperfusion.
 15. The method of claim 13, further comprising administering carbon dioxide in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion.
 16. The method of claim 13, further comprising monitoring reperfusion injury or microvascular obstructions using magnetic resonance imaging during reperfusion and post-reperfusion.
 17. A method for reducing hemorrhagic microvascular obstructions in a subject in need thereof comprising: (i) administering to the subject a first admixture comprising carbon dioxide in an amount to reach a predetermined partial pressure of carbon dioxide to induce hyperemia; (ii) administering to the subject a second admixture comprising oxygen in an amount to reach a predetermined partial pressure of oxygen; (iii) administering oxygen in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion, wherein administering oxygen in a block-wise manner comprises alternating the amounts of oxygen administered between any of 5 mmHg and 100 mgHg, 20 mmHg and 100 mmHg, 30 mmHg and 100 mmHg, 40 mmHg and 100 mmHg, 50 mmHg and 100 mmHg, 60 mmHg and 100 mmHg, 70 mmHg and 100 mmHg, 80 mmHg and 100 mmHg, 90 mmHg and 100 mmHg, 20 mmHg and 40 mmHg, 30 mmHg and 40 mmHg, 20 mmHg and 50 mmHg, 30 mmHg and 50 mmHg, 40 mmHg and 50 mmHg, 20 mmHg and 60 mmHg, 30 mmHg and 60 mmHg, 40 mmHg and 60 mmHg, or 50 mmHg and 60 mmHg of oxygen; and (iv)re-establishing perfusion to an ischemic area, so as to reduce hemorrhagic microvascular obstructions in the subject.
 18. The method of claim 17, further comprising establishing therapeutic hypothermia by cooling blood prior to reperfusion.
 19. The method of claim 17, further comprising administering carbon dioxide in a block-wise manner to the subject prior to re-establishing perfusion so as to adapt the subject for reperfusion.
 20. The method of claim 17, further comprising monitoring reperfusion injury or microvascular obstructions using magnetic resonance imaging during reperfusion and post-reperfusion. 